A non-aqueous electrolyte solution for storage battery devices contains a high-permittivity solvent such as a carbonate type solvent for good dissolution of an electrolyte salt. The carbonate type solvent is capable of particularly dissolving a lithium salt well to exhibit high lithium-ion conductivity and also has a wide potential window. Thus, the carbonate type solvent is suitably used for lithium-ion secondary batteries, lithium-metal secondary batteries, lithium primary batteries, electric double-layer capacitors, lithium-ion capacitors, and so on. However, when only a high-permittivity solvent such as a carbonate type solvent is used, the charge-discharge cycle life may be short.
So as a non-aqueous electrolyte solution excellent in cycle characteristics, by which storage battery devices having a long charge-discharge cycle life can be obtained, the following non-aqueous electrolyte solutions containing a hydrofluoroether which is excellent in stability to oxidative decomposition have been proposed:
(i) a non-aqueous electrolyte solution using, as the electrolyte solution, a hydrofluoroether represented by H—(CF2—CF2)a—CH2—O—CF2—CF2—H, wherein a is 1 or 2 (Patent Document 1);
(ii) a non-aqueous electrolyte solution comprising an acyclic hydrofluoroether which has a fluorination rate of at least 55% and which has at least one of —CF2H group or —CFH2 group at a terminal of e.g. HCF2CF2CH2OCF2CF2H or CF3CH2OCF2CF2H, and an organic solvent having a relative permittivity of at least 10, wherein in the electrolyte solution, the content of the acyclic hydrofluoroether is from 40 to 90 vol %, and the content of the organic solvent is from 5 to 50 vol % (Patent Document 2); and
(iii) a non-aqueous electrolyte solution, wherein a hydrofluoroether such as CF3CF2CH2OCF2CH3 is contained in the electrolyte solution, and the content of the hydrofluoroether is more than 30 vol % and at most 90 vol % (Patent Document 3).